Adjust "texture density" during UV mapping?
There are two ways:

1) classic; in edit mode select all vertices UV mapped, then open an UV image editor, select the wood texture, select all the UV grid and press S to scale it at the desired size.

2) If you don't want to modify the UV mapping, in the node material editor add an input UV node, plug it into a mapping node, and plug the latter in the vector input of the image texture node, then adjust the scale values.